A photocopying machine or image input terminal with a platen can be difficult to use with books, especially books with thick bindings. This problem is usually addressed by incorporation of a book edge at one edge of the platen, such as in the Xerox 5042 BookSaver Copier. This edge allows the half of the book not being copied to hang over the edge of the machine so that the book binding is not compressed against the platen, thereby protecting the book binding and allowing ease of page by page copying. As a book is copied from page to page, the book must be rotated by 180.degree. in the progression from left page to right page. This results in every other page having an inverted image with respect to the previous page. If no corrective action is taken, the output document pages from the copier or scanner are alternately inverted.
U.S. Pat. No. 4,727,397 to Stemmle addresses this issue for military style duplex copying, where the top to bottom alignment of images on a document is in a direction parallel to the path of travel of the sheet through the copier, by proposing that in a copier which is already provided with a duplex tray, the duplex tray can be arranged to rotate by 180.degree. for each sheet received therein, with the eventual result that upon completion of a set, on each side of the duplex document, the image has correct top to bottom orientation. While this is undoubtedly an effective method, it is somewhat mechanically cumbersome.
Image rotation is well known in the art of electronic copying, as taught, for example, in U.S. Pat. No. 4,703,515 to Baroody, Jr. wherein bitmap data representing an image can be rotated in a fairly efficient manner as required. That patent describes a significant number of rotation methods, which can accomplish bitmap rotation by 180.degree..
Less well known, but clearly available from the art, is the ability to rotate an image optically, or by lenses, prior to projecting the image onto either a sensor or a photoreceptor of a light lens copier. Thus, for example, as shown in the text, Modern Optical Engineering, "The Design of Optical Systems", by W. J. Smith, McGraw-Hill, the use of a Dove, Porro, or Abbe prism may be used to rotate the image as required.
It would be highly desirable to provide a digital or light lens copier mode of operation which automatically or in response to a simple control signal produces a collated copy set or electronic image set from a book at a book edge copying arrangement.